Soft discontinuous reception (soft drx)

ABSTRACT

Embodiments of the present disclosure are related to achieving better tradeoffs between battery saving and latency to, e.g., support ultra-low latency applications by introducing soft Discontinuous Reception (DRX). In some embodiments, a method of operation of a node in a wireless communications network comprises initiating transmission, during a DRX awake period, of control information to a wireless device on two or more control channel subsets during two or more time periods within the DRX awake period, respectively. The two or more control channel subsets are different subsets of a plurality of candidate control channels. In some embodiments, the two or more time periods are two or more subframes. The candidate control channels are control channels that the wireless device is configured to monitor. The two or more control channel subsets can be selected to, e.g., reduce latency while not increasing energy consumption as compared to legacy DRX.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 16/310,365, filed on Dec. 14, 2018, which is a National Stage Entryof PCT International Application No. PCT/IB2016/053623, filed on Jun.17, 2016, the disclosure and content of each of which are incorporatedherein by reference in their entireties.

TECHNICAL FIELD

The present disclosure relates to Discontinuous Reception (DRX) in awireless communications network.

BACKGROUND

For the sake of presentation, the technical background is explained withrespect to cellular networks that are implemented based on Long TermEvolution (LTE) and LTE-Advanced standards, both of which are generallyreferred to herein as LTE. Nevertheless, the present disclosure isgenerally applicable to any wireless communication network or anycellular communication network in which the wireless device supportsDiscontinuous Reception (DRX).

LTE Frame Structure

Orthogonal Frequency Division Multiplexing (OFDM) is used in LTE, wherethe radio resources are divided into OFDM symbols in the time domain andorthogonal narrowband sub-carriers in the frequency domain. The smallestradio frequency element in LTE resources is called a Resource Element(RE). A RE consists of one OFDM symbol in time that spans 66.7microseconds (μs) plus a normal or extended cycle prefix and onesub-carrier in frequency that spans 15 kilohertz (kHz). A RE can carryone modulation symbol. The smallest unit that can be scheduled to a UserEquipment device (UE) is defined as a Physical Resource Block (PRB)pair, which consists of 12 subcarriers in frequency and two slots intime, where each slot consists of six to seven OFDM symbols. A PRB pairspans one subframe in time, which has a duration of 1 millisecond (ms).

In LTE, the base station, called an enhanced or evolved Node B (eNB),schedules downlink transmissions to UEs on a per-subframe basis. Inaddition to transmitting the UE traffic data, the eNB needs to transmitDownlink Control Information (DCI) to UEs, which includes informationabout the location of the PRB pairs allocated to the UEs in the PhysicalDownlink Shared Channel (PDSCH), the type of modulation and coding thatthe UEs need to use for decoding the UEs' traffic data, as well as othercontrol information. In LTE Release 8, 9, and 10, DCI is conveyed onlyin a Physical Downlink Control Channel (PDCCH). A PDCCH is transmittedin the control region of the subframe, which is located at the beginningof the subframe (up to the first four OFDM symbols). In LTE Release 11,an enhanced PDCCH (ePDCCH) is introduced as described in ThirdGeneration Partnership Project (3GPP) Technical Specification (TS)36.211 V12.4.0, Section 6.8A, where DCI can also be transmitted in thedata region of the subframe that carries the data traffic for UEs.

Since the UE does not know a priori whether it is scheduled in aparticular subframe or not, the UE monitors the eNB downlinktransmission. Since the UE does not know the precise location within thesubframe of the DCI intended for the UE, the UE performs blind decoding,where the UE monitors all control channel candidates that may beassigned to the UE in the subframe. These control channel candidates arereferred to as PDCCH candidates (or ePDCCH candidates), and the UE mayreceive DCI on any of the PDCCH candidates (or ePDCCH candidates).

Discontinuous Reception

The UE is required to monitor its serving eNB's transmission in order toknow if there is downlink data intended for the UE. However,continuously monitoring the downlink channel results in high energyconsumption, which reduces the battery lifetime of the UE. In order toreduce energy consumption, Discontinuous Reception (DRX) is implementedwhere the UE goes into predefined Awake/Sleep periods to save batterylife. As used herein, the “DRX awake period” is a period of time duringwhich a wireless device operating according to a DRX scheme is awakeduring a DRX cycle. In 3GPP LTE, the DRX awake period includes one ormore of the following: On Duration Timer for long and short cycle, DRXInactivity Timer, and DRX Retransmission Timer, which are defined in3GPP TS 36.321 V12.4.0 in Section 3.1, as follows:

-   -   On Duration Timer: the number of consecutive PDCCH subframe(s)        where the UE is Awake at the beginning of a DRX cycle, whether        it is a long DRX cycle or a DRX short cycle, as shown in FIG. 1.    -   DRX Inactivity Timer: the number of consecutive PDCCH        subframe(s) where the UE is Awake after the subframe within        which a PDCCH indicates an initial uplink or downlink user data        transmission. Upon expiry of DRX Inactivity Timer and if short        DRX cycle is configured, short DRX cycle is used and DRX Short        Cycle Timer specifies the number of consecutive subframe(s)        where the short DRX cycle is followed.    -   DRX Retransmission Timer: when a retransmission is expected,        this parameter denotes the number of consecutive        PDCCH-subframe(s) where the UE is Awake until a downlink        retransmission is received.

The Awake state can be sometimes extended longer than the On DurationTimer. For example, the Awake state may be extended longer than the OnDuration Timer shown in FIG. 1 due to the detection of initial uplink ordownlink transmission which activate DRX Inactivity Timer, due to theactivation of short cycle if configured, due to the expectation ofpossible retransmission which may activate DRX Retransmission Timer,and/or during contention resolution in random access. When the UE is inthe Awake state, the UE decodes all control channel candidates todetermine whether there is data for the UE. For instance, for an LTE UEconfigured with PDCCH, the UE is expected to monitor a total of 22 PDCCHcandidates (i.e., sum of numbers in the last column in Table 1 below) inevery subframe where the UE is in the Awake state. The time-frequencylocations of the 22 PDCCH candidates are dependent on a Radio NetworkTemporary Identifier (RNTI) and the subframe number; however, the numberof PDCCH candidates that the UE monitor is the same (i.e., 22) in everysubframe during a DRX Awake period. On the other hand, when the UE is inthe Sleep state, the UE does not monitor or decode any channel, i.e.,the UE goes to sleep to save battery.

TABLE 1 PDCCH candidates monitored by a UE (reproduced from 3GPP TS36.213 V12.4.0, Table 9.1.1-1). Search space S_(k) ^((L)) NumberAggregation Size of PDCCH Type level L [in CCEs] candidates M^((L))UE-specific 1 6 6 2 12 6 4 8 2 8 16 2 Common 4 16 4 8 16 2

The battery gain achieved by using DRX comes at the expense of increaseddownlink latency, as transmission of packets that arrive at the eNB whenthe UE is in the Sleep state has to wait until the UE is in the Awakestate. For instance, the DRX long cycle may be 320 ms and the ONDuration Timer may be 10 ms. This results in a latency of up to 310 msfor a packet that arrives at the eNB when the UE is in the Sleep state.Such latency may not be acceptable for ultra-low latency applicationsthat are expected to be supported in next generation networks such ashealthcare and emergency notification systems.

SUMMARY

Embodiments of the present disclosure are related to achieving bettertradeoffs between battery saving and latency to, e.g., support ultra-lowlatency applications by introducing soft Discontinuous Reception (DRX).In some embodiments, a method of operation of a wireless device in awireless communications network comprises monitoring, during a DRX awakeperiod, two or more control channel subsets during two or more timeperiods within the DRX awake period, respectively. The two or morecontrol channel subsets are different subsets of a plurality ofcandidate control channels. In some embodiments, the two or more timeperiods are two or more subframes. The candidate control channels arecontrol channels that the wireless device is configured to monitor. Thetwo or more control channel subsets can be selected to, e.g., reducelatency while not increasing energy consumption as compared to legacyDRX.

In some embodiments, the wireless device supports downlink CarrierAggregation (CA), and the plurality of candidate control channelscomprise candidate control channels on at least two downlink carriers.In some embodiments, a first control channel subset of the two or morecontrol channel subsets comprises at least one candidate control channelon a first carrier of the at least two downlink carriers but not anycandidate control channels on a second carrier of the at least twodownlink carriers.

In some embodiments, the plurality of candidate control channelscomprises a first plurality of candidate Physical Downlink ControlChannels (PDCCHs) and a second plurality of candidate enhanced PDCCHs(ePDCCHs). Further, the two or more control channel subsets comprise afirst control channel subset that comprises at least some of the firstplurality of candidate PDCCHs but not any of the second plurality ofcandidate ePDCCHs, and a second control channel subset that comprises atleast some of the second plurality of candidate ePDCCHs but not any ofthe first plurality of candidate PDCCHs.

In some embodiments, at least one of the two or more control channelsubsets comprises one or more candidate control channels that utilize alow complexity modulation and coding scheme. In some embodiments, theone or more candidate control channels that utilize a low complexitymodulation and coding scheme are candidate control channels that utilizea modulation and coding scheme that is sufficient to carry only data toenable the wireless device to activate a DRX Inactivity Timer or toswitch to legacy DRX.

In some embodiments, the two or more control channel subsets consist oftwo control channel subsets.

In some embodiments, the two or more control channel subsets comprise afirst control channel subset that comprises all of the plurality ofcandidate control channels and a second control channel subset thatcomprises less than all of the plurality of candidate control channels.

In some embodiments, monitoring the two or more control channel subsetsduring the two or more time periods within the DRX awake period,respectively, comprises determining a first control channel subset for afirst time period within the DRX awake period, monitoring candidatecontrol channels in the first control channel subset during the firsttime period for a downlink control channel transmission to the wirelessdevice, determining a second control channel subset for a second timeperiod within the DRX awake period, and monitoring candidate controlchannels in the second control channel subset during the second timeperiod for a downlink control channel transmission to the wirelessdevice.

In some embodiments, the method further comprises receiving one or moresoft DRX parameters from a network node, the one or more soft DRXparameters comprising information that defines the two or more controlchannel subsets for the two or more time periods within the DRX awakeperiod, respectively. In some embodiments, receiving the one or moresoft DRX parameters from the network node comprises receiving a RadioResource Control (RRC) message from the network node comprising the oneor more soft DRX parameters. In some embodiments, the method furthercomprises sending capability information to the network node, thecapability information comprising an indication of whether the wirelessdevice supports soft DRX. In some embodiments, receiving the one or moresoft DRX parameters from the network node comprises receiving a MediumAccess Control (MAC) Control Element (CE) from the network nodecomprising the one or more soft DRX parameters. In some embodiments, themethod further comprises deciding to accept soft DRX activation uponreceiving the MAC CE, and sending an acceptance of soft DRX activationto the network node.

In some embodiments, the method further comprises sending a message toactivate soft DRX to a network node, and receiving a response from thenetwork node. In some embodiments, the message to activate soft DRXcomprises one or more soft DRX parameters comprising information thatdefines the two or more control channel subsets for the two or more timeperiods within the DRX awake period, respectively. In some embodiments,the message to activate soft DRX comprises one or more modifications toone or more soft DRX parameters comprising information that defines thetwo or more control channel subsets for the two or more time periodswithin the DRX awake period, respectively.

In some embodiments, a DRX offset for the wireless device is differentthan a DRX offset of another wireless device such that at least one ofthe two or more time periods within the DRX awake period of the wirelessdevice does not overlap with at least one respective time period withina DRX awake period of the other wireless device.

In some embodiments, the method further comprises sending a request todeactivate soft DRX to a network node.

In some embodiments, the method further comprises deactivating soft DRXin response to an occurrence of an external or internal event.

In some embodiments, the method further comprises receiving a request todeactivate soft DRX from a network node.

Embodiments of a wireless device for operation in a wirelesscommunications network are also disclosed. In some embodiments, thewireless device is adapted to monitor, during a DRX awake period, two ormore control channel subsets during two or more time periods within theDRX awake period, respectively, wherein the two or more control channelsubsets are different subsets of a plurality of candidate controlchannels. In some embodiments, the wireless device is further adapted tooperate according to any embodiment of the method of operation of awireless device disclosed herein.

In some embodiments, a wireless device for operation in a wirelesscommunications network comprises at least one transceiver, at least oneprocessor, and memory storing instructions executable by the at leastone processor whereby the wireless device is operable to monitor, duringa DRX awake period, two or more control channel subsets during two ormore time periods within the DRX awake period, respectively, wherein thetwo or more control channel subsets are different subsets of a pluralityof candidate control channels. In some embodiments, the wireless deviceis further adapted to operate according to any embodiment of the methodof operation of a wireless device disclosed herein.

In some embodiments, a wireless device for operation in a wirelesscommunications network comprises a monitoring module operable tomonitor, during a DRX awake period, two or more control channel subsetsduring two or more time periods within the DRX awake period,respectively, wherein the two or more control channel subsets aredifferent subsets of a plurality of candidate control channels. In someembodiments, the wireless device further comprises one or moreadditional modules operable to cause the wireless device to operateaccording to any embodiment of the method of operation of a wirelessdevice disclosed herein.

Embodiments of a method of operation of a node in a wirelesscommunications network are also disclosed. In some embodiments, themethod of operation of the node comprises initiating transmission,during a DRX awake period of a wireless device, of control informationto the wireless device in a time period within the DRX awake period ofthe wireless device on one or more control channels in one of at leasttwo control channel subsets. The at least two control channel subsetsare at least two different subsets of a plurality of candidate controlchannels that are configured for the wireless device for at least twotime periods within the DRX awake period of the wireless device,respectively. In some embodiments, the two or more time periods are twoor more subframes.

In some embodiments, the plurality of candidate control channelscomprises candidate control channels on at least two downlink carriers.In some embodiments, a first control channel subset of the two or morecontrol channel subsets comprises at least one candidate control channelon a first carrier of the at least two downlink carriers but not anycandidate control channels on a second carrier of the at least twodownlink carriers.

In some embodiments, the plurality of candidate control channelscomprises a first plurality of candidate PDCCHs, and a second pluralityof candidate ePDCCHs. Further, the two or more control channel subsetscomprise a first control channel subset that comprises at least some ofthe first plurality of candidate PDCCHs but not any of the secondplurality of candidate ePDCCHs, and a second control channel subset thatcomprises at least some of the second plurality of candidate ePDCCHs butnot any of the first plurality of candidate PDCCHs.

In some embodiments, at least one of the two or more control channelsubsets comprises one or more candidate control channels that utilize alow complexity modulation and coding scheme. In some embodiments, theone or more candidate control channels that utilize a low complexitymodulation and coding scheme are candidate control channels that utilizea modulation and coding scheme that is sufficient to carry only data toenable the wireless device to activate a DRX Inactivity Timer or toswitch to legacy DRX.

In some embodiments, the two or more control channel subsets consist oftwo control channel subsets.

In some embodiments, the two or more control channel subsets comprise afirst control channel subset that comprises all of the plurality ofcandidate control channels and a second control channel subset thatcomprises less than all of the plurality of candidate control channels.

In some embodiments, initiating transmission of control information tothe wireless device in the time period within the DRX awake period ofthe wireless device on one or more control channels in the one of atleast two control channel subsets comprises determining a first controlchannel subset for a first time period within the DRX awake period ofthe wireless device, initiating transmission of control information tothe wireless device in one or more candidate control channels in thefirst control channel subset during the first time period if thewireless device is scheduled in the first time period, determining asecond control channel subset for a second time period within the DRXawake period of the wireless device, and initiating transmission ofcontrol information to the wireless device in one or more candidatecontrol channels in the second control channel subset during the secondtime period if the wireless device is scheduled in the second timeperiod.

In some embodiments, the method further comprises initiatingtransmission of one or more soft DRX parameters to the wireless device,the one or more soft DRX parameters comprising information that definesthe two or more control channel subsets for the two or more time periodswithin the DRX awake period, respectively. In some embodiments,initiating transmission of the one or more soft DRX parameters to thewireless device comprises initiating transmission of a RRC message tothe wireless device comprising the one or more soft DRX parameters. Insome embodiments, the method further comprises receiving capabilityinformation of the wireless device where the capability informationcomprises an indication of whether the wireless device supports softDRX, and deciding whether to activate soft DRX for the wireless devicebased on the capability information of the wireless device. In someembodiments, initiating transmission of the one or more soft DRXparameters to the wireless device comprises initiating transmission of aMAC CE to the wireless device comprising the one or more soft DRXparameters.

In some embodiments, the method further comprises receiving a message toactivate soft DRX from the wireless device, deciding whether to acceptactivation of soft DRX, and initiating transmission of a response to thewireless device. In some embodiments, the message to activate soft DRXcomprises one or more soft DRX parameters comprising information thatdefines the two or more control channel subsets for the two or more timeperiods within the DRX awake period, respectively. In some embodiments,the message to activate soft DRX comprises one or more modification toone or more soft DRX parameters comprising information that defines thetwo or more control channel subsets for the two or more time periodswithin the DRX awake period, respectively.

In some embodiments, a DRX offset for the wireless device is differentthan a DRX offset of another wireless device such that at least one ofthe two or more time periods within the DRX awake period of the wirelessdevice does not overlap with at least one respective time period withina DRX awake period of the other wireless device.

In some embodiments, the method further comprises receiving a request todeactivate soft DRX from the wireless device.

In some embodiments, the method further comprises initiatingtransmission of a request to deactivate soft DRX to the wireless device.

Embodiments of a node for operation in a wireless communications networkare also disclosed. In some embodiments, the node is adapted to initiatetransmission, during a DRX awake period of a wireless device, of controlinformation to the wireless device in a time period within the DRX awakeperiod of the wireless device on one or more control channels in one ofat least two control channel subsets. The at least two control channelsubsets are at least two different subsets of a plurality of candidatecontrol channels that are configured for the wireless device for atleast two time periods within the DRX awake period of the wirelessdevice, respectively. In some embodiments, the node is further adaptedto operate according to any embodiment of a method of operation of anode disclosed herein.

In some embodiments, a node for operation in a wireless communicationsnetwork comprises at least one processor and memory storing instructionsexecutable by the at least one processor whereby the node is operable toinitiate transmission, during a DRX awake period of a wireless device,of control information to the wireless device in a time period withinthe DRX awake period of the wireless device on one or more controlchannels in one of at least two control channel subsets. The at leasttwo control channel subsets are at least two different subsets of aplurality of candidate control channels that are configured for thewireless device for at least two time periods within the DRX awakeperiod of the wireless device, respectively. In some embodiments, thenode is further adapted to operate according to any embodiment of amethod of operation of a node disclosed herein.

In some embodiments, a node for operation in a wireless communicationsnetwork comprises a transmission module operable to initiatetransmission, during a DRX awake period of a wireless device, of controlinformation to the wireless device in a time period within the DRX awakeperiod of the wireless device on one or more control channels in one ofat least two control channel subsets. The at least two control channelsubsets are at least two different subsets of a plurality of candidatecontrol channels that are configured for the wireless device for atleast two time periods within the DRX awake period of the wirelessdevice, respectively. In some embodiments, the node further comprisesone or more additional modules operable to cause the node to operateaccording to any embodiment of the method of operation of a nodedisclosed herein.

Those skilled in the art will appreciate the scope of the presentdisclosure and realize additional aspects thereof after reading thefollowing detailed description of the embodiments in association withthe accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawing figures incorporated in and forming a part ofthis specification illustrate several aspects of the disclosure, andtogether with the description serve to explain the principles of thedisclosure.

FIG. 1 illustrates an implementation of Discontinuous Reception (DRX) inwhich a wireless device goes into cycles of predefined Awake/Sleepdurations;

FIGS. 2A and 2B show legacy DRX and an example of soft DRX,respectively;

FIG. 3 illustrates one example of a wireless communications network inwhich embodiments of the present disclosure may be implemented;

FIG. 4 illustrates the operation of a wireless device and a base stationaccording to some embodiments of the present disclosure;

FIG. 5 illustrates one example in which soft DRX is enabled, oractivated, via, e.g., Radio Resource Control (RRC) signaling accordingto some embodiments of the present disclosure;

FIG. 6 illustrates one example in which soft DRX is enabled, oractivated, via, e.g., Medium Access Control (MAC) signaling according tosome embodiments of the present disclosure;

FIG. 7 illustrates another example in which soft DRX is enabled, oractivated, via, e.g., MAC signaling according to some embodiments of thepresent disclosure;

FIG. 8 is a flow chart that illustrates a process performed by a basestation according to some embodiments of the present disclosure;

FIG. 9 is a flow chart that illustrates a process performed by awireless device according to some embodiments of the present disclosure;

FIG. 10 illustrates a plot of all feasible values of n₁ (the number ofsubframes where the wireless device is Awake and it is expected tomonitor a first control channel subset using soft DRX) and n₂ (number ofsubframes where the wireless device is Awake and it is expected tomonitor the second control channel subset using soft DRX) that satisfytwo constraints according to some example embodiments of the presentdisclosure;

FIGS. 11A and 11B provide an illustration of the soft DRX profilecompared to legacy DRX profile for an example in which n₁=5 and n₂=10;

FIGS. 12A and 12B show the soft DRX profiles of two wireless devices,assuming that both wireless devices use the soft DRX profile shown inFIG. 11B;

FIGS. 13 and 14 are block diagrams of example embodiments of a wirelessdevice; and

FIGS. 15 to 17 are block diagrams of example embodiments of a networknode.

DETAILED DESCRIPTION

The embodiments set forth below represent information to enable thoseskilled in the art to practice the embodiments and illustrate the bestmode of practicing the embodiments. Upon reading the followingdescription in light of the accompanying drawing figures, those skilledin the art will understand the concepts of the disclosure and willrecognize applications of these concepts not particularly addressedherein. It should be understood that these concepts and applicationsfall within the scope of the disclosure and the accompanying claims.

Radio Node: As used herein, a “radio node” is either a radio access nodeor a wireless device.

Radio Access Node: As used herein, a “radio access node” is any node ina radio access network of a wireless communications network thatoperates to wirelessly transmit and/or receive signals. Some examples ofa radio access node include, but are not limited to, a base station(e.g., an enhanced or evolved Node B (eNB) in a Third GenerationPartnership Project (3GPP) Long Term Evolution (LTE) network), ahigh-power or macro base station, a low-power base station (e.g., amicro base station, a pico base station, a home eNB, or the like), and arelay node.

Core Network Node: As used herein, a “core network node” is any type ofnode in a core network. Some examples of a core network node include,but are not limited to, e.g., a Mobility Management Entity (MME), aPacket Data Network (PDN) Gateway (P-GW), a Service Capability ExposureFunction (SCEF), or the like.

Wireless Device: As used herein, a “wireless device” is any type ofdevice that has access to (i.e., is served by) a wireless communicationsnetwork by wirelessly transmitting and/or receiving signals to a radioaccess node(s). Some examples of a wireless device include, but are notlimited to, a User Equipment device (UE) in a 3GPP network and a MachineType Communication (MTC) device.

Network Node: As used herein, a “network node” is any node that iseither part of the radio access network or the core network of awireless communications network/system.

Note that the description given herein focuses on a 3GPP wirelesscommunications system and, as such, 3GPP LTE terminology or terminologysimilar to 3GPP LTE terminology is oftentimes used. However, theconcepts disclosed herein are not limited to LTE or a 3GPP system.

Note that, in the description herein, reference may be made to the term“cell;” however, particularly with respect to Fifth Generation (5G)concepts, beams may be used instead of cells and, as such, it isimportant to note that the concepts described herein are equallyapplicable to both cells and beams.

Legacy Discontinuous Reception (DRX): A technique where a wirelessdevice can monitor its control channel candidates discontinuously basedon predefined Awake/Sleep periods.

Soft DRX: As used herein, “soft DRX” is a DRX technique in which awireless device monitors, during a DRX awake period, two or more controlchannel subsets during two or more time periods within the DRX awakeperiod, respectively. The two or more control channel subsets aredifferent subsets of multiple candidate control channels for thewireless device. The candidate control channels are a set of controlchannels that the wireless device is configured to monitor.

DRX Awake Period: As used herein, the “DRX awake period” is a period oftime during which a wireless device operating according to a DRX schemeis awake during a DRX cycle. In 3GPP LTE, the DRX awake period includesone or more of the following: On Duration Timer for long and shortcycle, DRX Inactivity Timer, and DRX Retransmission Timer.

Legacy Wireless Device: The term “legacy wireless device” as used hereinrefers to a wireless device (e.g., an LTE UE) that supports legacy DRX.

Enhanced Wireless Device: The term “enhanced wireless device” or“enhanced UE” as used herein refers to a wireless device (e.g., an LTEUE) that supports soft DRX.

Embodiments of the present disclosure that are presented herein aregenerally applicable to any wireless network in which the wirelessdevice supports DRX.

Embodiments of the present disclosure are related to achieving bettertradeoffs between battery saving and latency to, e.g., support ultra-lowlatency applications by introducing soft DRX. Unlike legacy DRX wherepower consumption of a wireless device (e.g., an LTE UE) alternatesroughly between two discreet power levels corresponding to Awake statesand Sleep states, in soft DRX, the power consumption levels of thewireless device can be a set of more than two discreet power levels orultimately resemble continuous functions. By allowing more powerconsumption levels, the wireless device can be Awake for longer timeswith the same total energy consumption achieved by legacy DRX. Toillustrate this, FIGS. 2A and 2B show approximation of the powerconsumed by monitoring control channel candidates for legacy DRX and anexample of soft DRX, respectively. The energy consumption due tomonitoring control channel candidates of each scheme during the Awakestate can be well approximated by the area of the square representingthe DRX awake period or Awake state of the legacy DRX and the area ofthe triangle representing the DRX awake period or Awake state for thesoft DRX example. By examining the areas for both schemes, it can beshown that both schemes consume the same amount of energy in thisexample. However, the DRX awake period or duration of the Awake statefor the soft DRX example is twice that of the legacy DRX example. Assuch, the maximum downlink latency for the soft DRX is reduced ascompared to that of the legacy DRX while at the same time energyconsumption is not increased (i.e., stays the same in this example).Note that DRX Inactivity Timer, DRX Retransmission Timer, and DRX shortcycle are not shown FIGS. 2A and 2B.

In some embodiments, the energy consumption level is varied in differenttime periods (e.g., subframes) within the DRX awake period (i.e., withinthe Awake state) by varying the number of candidate control channelsthat the wireless device monitors during different time periods (e.g.,subframes) within the DRX awake period (i.e., during the Awake state).In some embodiments, the energy consumption level is additionally oralternatively varied by restricting the set of control channels tomonitor to specific Orthogonal Frequency Division Multiplexing (OFDM)symbols. For instance, a triangle-like power shape such as thatillustrated in FIG. 2B can be approximated by gradually monitoring morecandidate control channels in every subframe during the DRX awake perioduntil the maximum power is reached, and then gradually monitoring lesscandidate control channels in every subframe of the DRX awake perioduntil the wireless device goes to sleep. However, this is only oneexample. Other non-limiting examples are described below.

In some embodiments, a network node (e.g., a base station such as aneNB) varies the soft DRX pattern (e.g., control channel subsets to bemonitored during different time periods (e.g., subframes) within the DRXAwake period) of a wireless device. In addition, in some embodiments, anetwork node (e.g., a base station such as an eNB) controls a wirelessdevice to switch between legacy DRX and soft DRX depending on, e.g.,other events such as network load, traffic type, and requests from thewireless device.

While not being limited to or by any particular advantage, embodimentsof the present disclosure provide a number of advantages over legacyDRX. For example, soft DRX may be used to reduce downlink latencyintroduced by legacy DRX without increasing the energy consumption atthe wireless device, which makes it attractive for ultra-low latencyapplications that are expected to be supported in next generationnetworks such as healthcare and emergency notification systems.

A wireless network is considered herein where base stations are used toserve wireless devices. Without loss of generality, the descriptionprovided herein focuses on a single cell scenario where a single basestation is used to communicate with a single wireless device; however,the present disclosure is not limited thereto. In this regard, FIG. 3illustrates one example of a wireless communications network 10 in whichembodiments of the present disclosure may be implemented. Asillustrated, the wireless communications network 10 includes a RadioAccess Network (RAN) 12 (e.g., an Evolved Universal Terrestrial RAN(EUTRAN)) including a number of base stations 14 (e.g., LTE eNBs)serving corresponding cells 16. Wireless devices 18 (e.g., LTE UEs)wirelessly transmit and receive signals to and from the base stations14, as will be appreciated by one of ordinary skill in the art. The basestations 14 may more generally be referred to as radio access nodes. Thebase stations 14 may be connected to one another via abase-station-to-base-station interface (e.g., an X2 interface) andconnected to a core network 20 (e.g., an Evolved Packet Core (EPC)) viarespective core network interfaces (e.g., S1 interfaces). The corenetwork 20 includes a number of core network nodes such as, for example,MMEs, P-GWs, Serving Gateways (S-GWs), etc., as will be appreciated byone of ordinary skill in the art.

The base station 14 is assumed to have configured the wireless device(s)18 that it serves with DRX. In LTE, such configuration is performed by aRadio Resource Control (RRC) message called a RRC reconfigurationmessage. This RRC message includes a number of DRX parameters that thewireless device 18 needs to use for DRX such as DRX ON duration, longcycle length, DRX Inactivity Timer, DRX Retransmission Timer, shortcycle length, short cycle timer, DRX Start offset, etc. The base station14 and the wireless device 18 will be synchronized in terms of DRXstates, i.e., the base station 14 knows precisely when the wirelessdevice 18 is in the Awake state and when the wireless device 18 is inthe Sleep state. As mentioned before, a legacy wireless device isrequired to monitor all control channel candidates that may be assignedto it for every subframe when it is in the Awake state. For instance, inLTE, legacy LTE UEs configured with Physical Downlink Control Channel(PDCCH) are required to monitor 22 PDCCH candidates in every subframe inthe Awake state.

FIG. 4 illustrates the operation of a wireless device 18 and a basestation 14 according to some embodiments of the present disclosure. Notethat optional steps are indicated by dashed lines. As illustrated, thebase station 14 and the wireless device 18 communicate with one anotherto enable soft DRX (step 100). In other words, the base station 14 andthe wireless device 18 communicate to establish an agreement to use softDRX. While this can be done using any suitable procedure, soft DRX isenabled via RRC signal in some example embodiments and enabled viaMedium Access Control (MAC) signaling in some other example embodiments.

Assuming that soft DRX is enabled, during the DRX awake period, thewireless device 18 monitors two or more control channel subsets duringtwo or more time periods (e.g., two or more subframes) within the DRXawake period, respectively (step 102). In other words, rather thanmonitoring all candidate control channels for a transmission of DownlinkControl Information (DCI) to the wireless device 18 in all time periods(e.g., all subframes) within the DRX awake period as is done by legacywireless devices, the wireless device 18 monitors different controlchannel subsets during different time periods (e.g., differentsubframes) within the DRX awake period. As used herein, a “controlchannel subset” is a subset of a defined set of candidate controlchannels that may be assigned to the wireless device 18. More precisely,as used herein, a “control channel subset” is a subset of a defined setof candidate control channels (CC_Candidate_Set) that may be assigned tothe wireless device 18, which can be denoted asCC_Subset⊆CC_Candidate_Set, where CC_Subset is the control channelsubset and CC_Candidate_Set is the set of candidate control channels. Afirst control channel subset is “different” than a second controlchannel subset if any candidate control channel included in the firstcontrol channel subset is not also included in the second controlchannel subset or vice versa. As an example, if the first controlchannel subset is {CC1, CC2, CC3} and the second control channel subsetis {CC1, CC2}, then the two control channel subsets are different eventhough they have two candidate control channels in common.

Thus, rather than monitoring all candidate control channels for, e.g., aPDCCH transmission intended for the wireless device 18, the wirelessdevice 18 monitors different control channel subsets in different timeperiods (e.g., subframes) within the DRX awake period. For example, inone time period (e.g., subframe), the wireless device 18 may monitor allof the candidate control channels; and, in another time period (e.g.,another subframe), the wireless device 18 may monitor less than all ofthe candidate control channels, thereby reducing energy consumption.

Unlike legacy DRX where the wireless device's power consumptionalternates roughly between two discreet power levels corresponding toAwake states and Sleep states, in soft DRX, the wireless device's powerconsumption levels can be a set of more than two discreet power levelsor ultimately resemble continuous functions. By allowing more powerconsumption levels, the wireless device can be Awake for longer timeswith the same total energy consumption achieved by legacy DRX, asillustrated in FIGS. 2A and 2B. As stated previously, the energyconsumption for a certain period of time during the Awake state can bemeasured by the area under power curves during that period of time. Insome embodiments, soft DRX is configured to keep the area under thepower curve less than or equal to the area of legacy DRX, whileextending the time of the Awake state.

Varying the energy consumption levels in different subframes in theAwake state is achieved by varying the number of control channels thatthe wireless device 18 has to monitor. In particular, the set of controlchannel candidates can be divided into subsets (possibly overlappingsubsets), where monitoring each subset leads to a particular powerconsumption level. Thus, by designing the subsets and assigningdifferent subsets to different subframes in the Awake state, the powerconsumption level of the wireless device 18 can be varied over the Awakestate. The following are some examples for designing control channelsubsets that result in reduced power consumption by the wireless device18 in the Awake state (i.e., the DRX awake period):

-   -   Some subsets may include less control channel candidates in a        narrowband, which reduces the power consumption.    -   Some subsets may include control channel candidates that are        restricted in time, e.g., restricted to one OFDM symbol period,        so the wireless device 18 can sleep early in the subframe.    -   For wireless devices 18 that are configured with Carrier        Aggregation (CA), i.e., allowed to receive data in more than one        carrier, some subsets may include only the control channels in a        subset of the carriers that the wireless device 18 should        monitor. For example, a wireless device 18 that is configured        with two carriers for downlink CA can have two control channel        subsets as follows: the first subset includes all control        channels in both carriers and the second subset includes the        control channels in only the primary carrier. By having some        subsets that include only the control channels in a subset of        the carriers that the wireless device 18 should monitor, the        wireless device 18 can turn off some of the circuitry that is        used to monitor the second carrier when it is required to        monitor the second subset, thereby reducing power consumption.        In 5G, it is envisioned that the wireless device 18 will be        configured with a large number of carriers in separate bands;        thus, soft DRX may be particularly advantageous in 5G wireless        communications networks. As another example, a wireless device        18 that is configured with three carriers for downlink CA can        have three control channel subsets as follows: a first subset        includes (e.g., all) control channel candidates in the first        carrier, the second subset includes (e.g., all) control channel        candidates of the second carrier, and a third subset that        includes (e.g., all) control channel candidates of the third        carrier. As another example, a wireless device 18 that is        configured with three carriers for downlink CA can have four        control channel subsets as follows: a first subset includes        (e.g., all) control channel candidates of all three carriers,        the second subset includes (e.g., all) control channel        candidates of the first carrier, a third subset that includes        (e.g., all) control channel candidates of the second carrier,        and a fourth subset that includes (e.g., all) control channel        candidates of the third carrier.    -   If a wireless device 18 is capable of receiving control        information in PDCCH and enhanced PDCCH (ePDCCH) types and the        implementation of the wireless device 18 requires different        power consumptions for PDCCH as compared to ePDCCH, then one can        vary the power consumption by varying the type of control        channels in the subsets. For instance, one subset may include        some or all of the PDCCH channel candidates (but, e.g., none of        the ePDCCH control channel candidates), and another subset may        include some or all ePDCCH control channel candidates (but,        e.g., none of the PDCCH control channel candidates).    -   Some control channels may be designed to have a less        sophisticated modulation and encoding scheme (i.e., a low        complexity modulation and coding scheme) so it requires less        power to decode them. Such control channels may carry less        control information. For instance, such control channels may        carry a very small amount of control information that is        sufficient to allow the wireless device 18 to activate its DRX        Inactivity Timer or to move to legacy DRX. A “low complexity”        modulation and coding scheme is a modulation and coding scheme        that requires less power consumption at the wireless device 18        to perform the demodulation and decoding since it requires less        computational steps. For instance, one bit may be sent with        repetition coding, which is much easier to decode than several        bits encoded with convolutional coding.

Similarly, during the DRX awake period (i.e., the Awake state) of thewireless device 18, the base station 14 transmits DCI to the wirelessdevice 18 in a time period (e.g., subframe) within the DRX awake periodof the wireless device 18 on one or more control channels (e.g., one ormore PDCCHs) from one of the two or more control channel subsets that ismonitored by the wireless device 18 during that time period (step 104).In other words, for a particular time period within the DRX awakeperiod, the wireless device 18 monitors a respective control channelsubset. Thus, assuming that the wireless device 18 is to be scheduledduring that time period, the base station 14 transmits DCI to thewireless device 18 using one or more of the control channels in thecontrol channel subset being monitored by the wireless device 18 duringthat time period.

Optionally, the wireless device 18 processes any received DCI, as willbe appreciated by one of ordinary skill in the art (step 106). Forexample, if the DCI indicates downlink resources scheduled for adownlink data transmission to the wireless device 18 in the time period,then the wireless device 18 receives that downlink data transmission inaccordance with the DCI.

When enabling, or activating, soft DRX in step 100 of FIG. 4, one ormore soft DRX parameters may be configured for the wireless device 18.In some embodiments, in addition to the legacy DRX parameters, the softDRX parameters may include one or more of the following:

-   -   One or more parameters that indicate the types of Awake periods        which soft DRX should be used. For instance, one or more soft        DRX parameters may specify whether soft DRX should be used for        one or more of the following types of Awake periods: long cycle        On Duration Timer, short cycle On Duration Timer, DRX Inactivity        Timer, and/or DRX Retransmission Timer. The rest of the        parameters below can be applied to all types of Awake periods or        they can be specified for each type of Awake period separately.        For instance, it may be desired to apply soft DRX only in long        cycle On Duration Timer, and use legacy DRX for short cycle On        Duration Timer, DRX Inactivity Timer, and DRX Retransmission        Timer; in this case, the parameters below will be used only for        long cycle On Duration Timer.    -   A soft DRX parameter that indicates the number of control        channel candidate subsets        -   The number of control channel candidate subsets can be any            integer greater than or equal to 1. However, for simplicity,            it may be beneficial to restrict the set of possible numbers            of control channel candidate subsets; e.g., this set can be            {1, 2, 4, 6} and, in this case, two bits are sufficient to            indicate the number of control channel candidate subsets.    -   One or more soft DRX parameters that, for each control channel        subset, indicate:        -   The control channel candidates that belong to the control            channel subset.            -   A control channel subset can include any set of the                candidate control channels. However, for simplicity, it                may be beneficial to restrict the set of possible                control channel candidates for each subset in order to                reduce the number of bits needed to indicate which                control channel candidates belongs to each subset. For                example, the control channel candidates can be one of                the following four possibilities which requires two bits                per subset: fall control channel candidates, first half                of control channel candidates, second half of control                channel candidates, control channel candidates with even                indices}.        -   The subframes where this control channel subset should be            used.            -   A control channel subset can be indicated to be used for                any set of one or more subframes. However, for                simplicity, it may be beneficial to restrict the set of                possible subframes for each control channel subset in                order to reduce the number of bits needed to indicate                which subframe(s) belongs to each control channel                subset. For example, the subframes can be one of the                following four possibilities which require two bits per                subset: {first half of subframes in the awake period,                second half of subframes in the awake period, first 70%                of subframes in the awake period, last 30% of subframes                in the awake period}.

An alternative way to simplify the exchange of soft DRX parameters is todefine soft DRX profiles which are known a priori to both the basestation 14 and the wireless device 18, e.g., stored in a lookup table,where each profile includes different soft DRX parameters. This way,only the index of the soft DRX profile can be exchanged to configuresoft DRX.

FIGS. 5 through 7 illustrate example embodiments of step 100 of FIG. 4.In particular, FIG. 5 illustrates one example in which soft DRX isenabled, or activated, via, e.g., RRC signaling according to someembodiments of the present disclosure. As illustrated, the wirelessdevice 18 sends capability information to the base station 14 (step200). This capability information includes an indication as to whetherthe wireless device 18 supports soft DRX. In some embodiments, thewireless device 18 sends its capability information to the base station14 during RRC connection establishment. For existing LTE UEs, capabilityinformation may be modified to include an indication of whether the LTEUE supports soft DRX.

The base station 14 decides whether to activate soft DRX based on thecapability information of the wireless device 18 (step 202). Inparticular, if both the wireless device 18 and the base station 14support soft DRX, then the base station 14 decides to activate soft DRX.Otherwise, the base station 14 decides not to activate soft DRX.Assuming that the base station 14 decides to activate soft DRX, the basestation 14 sends one or more soft DRX parameters to the wireless device18, e.g., in an RRC message (step 204). In some embodiments, the basestation 14 sends an RRC reconfiguration message to the wireless device18, where the RRC reconfiguration message indicates to the wirelessdevice 18 that soft DRX is to be activated with one or more soft DRXparameters specified in the RRC reconfiguration message. The one or moresoft DRX parameters may include, for example, an indication of the twoor more control channel subsets to be monitored by the wireless device18 and the two or more respective time periods in which the two or morecontrol channel subsets are to be monitored. For example, for eachsubframe in the DRX awake period, the one or more soft DRX parametersmay include an indication of the control channel subset to be monitoredby the wireless device 18 in that subframe.

Optionally, at some point after activating soft DRX, the base station 14may decide to deactivate soft DRX (step 206). This decision may be madebased on any suitable criteria such as, for example, the occurrence ofparticular one or more events, such as change in traffic, number ofconnected wireless devices, wireless device's battery status, etc. Thebase station 14 then sends a message to the wireless device 18instructing the wireless device 18 to deactivate soft DRX (step 208).This message may again be sent via RRC signaling (e.g., an RRCreconfiguration message).

FIG. 6 illustrates one example in which soft DRX is enabled, oractivated, via, e.g., MAC signaling according to some embodiments of thepresent disclosure. As illustrated, the wireless device 18 sends amessage to the base station 14 requesting activation of soft DRX (step300). In some embodiments, this message is provided via a MAC ControlElement (CE) that includes one or more desired soft DRX parameters orone or more desired modifications to pre-existing soft DRX parameters.Again, the one or more soft DRX parameters may include, for example, anindication of the two or more control channel subsets to be monitored bythe wireless device 18 and the two or more respective time periods inwhich the two or more control channel subsets are to be monitored.

The base station 14 decides whether to accept soft DRX activation (step302). This decision may be based on any suitable criteria such as, forexample, the capability of the base station 14 to support soft DRX,number of connected wireless devices, and traffic conditions, etc. Thebase station 14 sends a message either accepting or rejecting soft DRXactivation as decided in step 302 (step 304). In some embodiments, themessage accepting or rejecting soft DRX activation may be sent via a MACCE. While not illustrated, the wireless device 18 (and the base station14) will use soft DRX if activation of soft DRX is accepted or not usesoft DRX if activation of soft DRX is rejected.

Optionally, the base station 14 and/or the wireless device 18 maysubsequently decide to deactivate soft DRX, in which case appropriatecommunication is performed to deactivate soft DRX. For example, at somepoint after activating soft DRX, the base station 14 may decide todeactivate soft DRX (step 306). This decision may be made based on anysuitable criteria such as, for example, the occurrence of particular oneor more events, such as change in traffic, number of connected wirelessdevices, wireless device's battery status, etc. The base station 14 thensends a message to the wireless device 18 instructing the wirelessdevice 18 to deactivate soft DRX (step 308). This message may again besent via a MAC CE. Alternatively, at some point after activating softDRX, the wireless device 18 may decide to deactivate soft DRX (step310). This decision may be made based on any suitable criteria such as,for example, the occurrence of particular one or more events, such aschange in traffic, number of connected wireless devices, wirelessdevice's battery status, etc. The wireless device 18 then sends amessage to the base station 14 requesting deactivation of soft DRX (step312). This message may again be sent via a MAC CE. Further, the requestfor deactivation may, in some embodiments, be either accepted orrejected by the base station 14.

FIG. 7 illustrates another example in which soft DRX is enabled, oractivated, via, e.g., MAC signaling according to some embodiments of thepresent disclosure. As illustrated, the base station 14 sends a messageto the wireless device 18 requesting activation of soft DRX (step 400).In some embodiments, this message is provided via a MAC CE that includesone or more desired soft DRX parameters or one or more desiredmodifications to pre-existing soft DRX parameters. Again, the one ormore soft DRX parameters may include, for example, an indication of thetwo or more control channel subsets to be monitored by the wirelessdevice 18 and the two or more respective time periods in which the twoor more control channel subsets are to be monitored.

The wireless device 18 decides whether to accept soft DRX activation(step 402). This decision may be based on any suitable criteria such as,for example, the capability of the wireless device 18 to support softDRX, number of connected wireless devices, and traffic conditions, etc.The wireless device 18 sends a message either accepting or rejectingsoft DRX activation as decided in step 402 (step 404). In someembodiments, the message accepting or rejecting soft DRX activation maybe sent via a MAC CE. While not illustrated, the base station 14 (andthe wireless device 18) will use soft DRX if activation of soft DRX isaccepted or not use soft DRX if activation of soft DRX is rejected.

Optionally, the base station 14 and/or the wireless device 18 maysubsequently decide to deactivate soft DRX, in which case appropriatecommunication is performed to deactivate soft DRX. For example, at somepoint after activating soft DRX, the base station 14 may decide todeactivate soft DRX (step 406). This decision may be made based on anysuitable criteria such as, for example, the occurrence of particular oneor more events, such as change in traffic, number of connected wirelessdevices, wireless device's battery status, etc. The base station 14 thensends a message to the wireless device 18 instructing the wirelessdevice 18 to deactivate soft DRX (step 408). This message may again besent via a MAC CE. Alternatively, at some point after activating softDRX, the wireless device 18 may decide to deactivate soft DRX (step410). This decision may be made based on any suitable criteria such as,for example, the occurrence of particular one or more events, such aschange in traffic, number of connected wireless devices, wirelessdevice's battery status, etc. The wireless device 18 then sends amessage to the base station 14 requesting deactivation of soft DRX (step412). This message may again be sent via a MAC CE. Further, the requestfor deactivation may, in some embodiments, be either accepted orrejected by the base station 14.

FIG. 8 is a flow chart that illustrates step 104 of FIG. 4 in moredetail according to some embodiments of the present disclosure. Notethat while the process is described as including a number of “steps,”the “steps” may be performed in any order or some of the steps may beperformed in parallel unless otherwise indicated or required. Asillustrated, the base station 14 initializes a subframe index i to, inthis example, 1 (step 500). When the subframe index i is 1, the subframeindex i refers to the first subframe in the DRX awake period of thewireless device 18. Likewise, a subframe index i equal to 2 refers tothe second subframe in the DRX awake period of the wireless device 18.

The base station 14 determines a control channel subset to be monitoredby the wireless device 18 during the i-th subframe of the DRX awakeperiod of the wireless device 18 based on the soft DRX parametersconfigured for the wireless device 18 (i.e., based on the soft DRXconfiguration of the wireless device 18) (step 502). In someembodiments, the control channel subset for the i-th subframe of the DRXawake period may be determined based on the soft DRX parametersconfigured for the wireless device 18, subframe number, and optionally awireless device (e.g., UE) identifier (e.g., RNTI). The base station 14also determines whether the wireless device 18 is to be scheduled forthe i-th subframe of the DRX awake period of the wireless device 18(step 504). If not, the process proceeds to step 508. However, if thewireless device 18 is to be scheduled in the i-th subframe of the DRXawake period, the base station 14 transmits DCI in one or more controlchannels that are in the control channel subset to be monitored by thewireless device 18 for the i-th subframe (step 506). In this manner, thebase station 14 limits the control channel(s) on which the DCI istransmitted to the wireless device 18 to those being monitored by thewireless device 18 in the i-th subframe.

Whether proceeding from the NO decision in step 504 or from step 506,the base station 14 determines whether the i-th subframe is the lastsubframe in the DRX awake period of the wireless device 18 (step 508).If so, the process ends. Otherwise, the base station 14 increments thesubframe index i (step 510), and the process returns to step 502 and isrepeated for the next subframe. Using the process of FIG. 8, the basestation 14 operates to, in each subframe in which the wireless device 18is awake, determine the control channel subset to be monitored by thewireless device 18 in that subframe and, if appropriate, transmit DCI tothe wireless device 18 in that subframe on one or more of the controlchannels in the control channel subset being monitored by the wirelessdevice 18.

FIG. 9 is a flow chart that illustrates step 102 of FIG. 4 in moredetail according to some embodiments of the present disclosure. Notethat while the process is described as including a number of “steps,”the “steps” may be performed in any order or some of the steps may beperformed in parallel unless otherwise indicated or required. Asillustrated, the wireless device 18 initializes a subframe index i to,in this example, 1 (step 600). When the subframe index i is 1, thesubframe index i refers to the first subframe in the DRX awake period ofthe wireless device 18. Likewise, a subframe index i equal to 2 refersto the second subframe in the DRX awake period of the wireless device18.

The wireless device 18 determines a control channel subset to bemonitored by the wireless device 18 during the i-th subframe of the DRXawake period of the wireless device 18 based on the soft DRX parametersconfigured for the wireless device 18 (i.e., based on the soft DRXconfiguration of the wireless device 18), subframe number, andoptionally based on a wireless device (e.g., UE) identifier such as anRNTI (step 602). In some embodiments, the control channel subset to bemonitored by the wireless device 18 during the i-th subframe of the DRXawake period may be determined based on the soft DRX parametersconfigured for the wireless device 18, subframe number, and optionally awireless device (e.g., UE) identifier (e.g., RNTI). The wireless device18 then monitors the candidate control channels in the determinedcontrol channel subset for the i-th subframe of the DRX awake period(step 604). In some embodiments, this monitoring is or at least includesblind decoding over all of the candidate control channels in the controlchannel subset determined for the i-th subframe. In this manner, ratherthan monitoring all possible candidate control channels in allsubframes, the wireless device 18 monitors only those candidate controlchannels in the control channel subset configured for the particularsubframe.

The wireless device 18 determines whether the i-th subframe is the lastsubframe in the DRX awake period of the wireless device 18 (step 606).If so, the process ends. Otherwise, the wireless device 18 incrementsthe subframe index i (step 608), and the process returns to step 602 andis repeated for the next subframe. Using the process of FIG. 9, thewireless device 18 operates to, in each subframe in which the wirelessdevice 18 is awake, determine the control channel subset to be monitoredby the wireless device 18 in that subframe and monitor only thosecandidate control channels in the determined control channel subset.

A simple and practical embodiment of soft DRX can be constructed bydividing the set of candidate control channels that the wireless device18 is supposed to monitor into two control channel subsets. Each ofthese two control channel subsets is assigned to a respective subset ofthe subframes in the DRX awake period of the wireless device 18. Onespecific example of this embodiment is described below with respect toFIG. 10 and FIGS. 11A and 11B. To facilitate the discussion, followingssymbols are defined:

Symbol Definition P₁ the power required by the wireless device tomonitor the first control channel subset using soft DRX P₂ the powerrequired by the wireless device to monitor the second control channelsubset using soft DRX P_(legacy) the power required by the wirelessdevice to monitor all control channel candidates using legacy DRX n₁Number of subframes where the wireless device is Awake and it isexpected to monitor the first control channel subset using soft DRX n₂Number of subframes where the wireless device is Awake and it isexpected to monitor the second control channel subset using soft DRXn_(legacy) Number of subframes where the wireless device is Awake and itis expected to monitor all control channel candidates using legacy DRX

One can design soft DRX to insure that it results in the same or lessenergy while making the wireless device 18 stay awake for longer orsimilar duration as compared to legacy DRX by satisfying the followingequations:

n ₁ P ₁ +n ₂ P ₂ ≤n _(legacy) P _(legacy), (Energy constraint)

n ₁ +n ₂ ≥n _(legacy). (Awake period constraint)

Example 1: Assume the first and second control channel subsets arechosen such that the first control channel subset is the same as legacyDRX while the second control channel subset requires only 50% of thepower to be monitored, i.e., P₁=P_(legacy) and P₂=0.5 P_(legacy). Thefirst control channel subset provides the base station 14 the sameflexibility in scheduling the wireless device 18 as compared to legacyDRX, as the wireless device 18 is expected to decode all control channelcandidates. However, the second control channel subset provides the basestation 14 with less flexibility as the wireless device 18 is expectedto monitor fewer candidate control channels. Further, assume the Awakeperiod of the legacy DRX is ten subframes.

In FIG. 10, all feasible values of n₁ and n₂ that satisfy the twoconstraints above are plotted. The constraint lines are also shown inFIG. 10. Higher values of n₂ result in more battery saving and lesslatency, but lower scheduling flexibility. On the other hand, highervalues of n₁ result in less battery saving and more latency, but higherscheduling flexibility. Hence, in choosing n₁ and n₂, it is important tohave good tradeoff between battery saving, latency, and schedulingflexibility.

One example solution is to have n₁=5 and n₂=10, which results in thesame energy consumption of legacy DRX but with a total awake period of15 subframes, i.e., 50% more than legacy DRX. The gain comes at theexpense that the base station 14 will have the same flexibility ofscheduling the wireless device 18 as compared to legacy DRX for onlyfive subframes instead of ten subframes. An illustration of the soft DRXprofile compared to the legacy DRX profile for n₁=5 and n₂=10 is shownin FIGS. 11A and 11B.

The embodiment described above for two control channel subsets can begeneralized by dividing the set of candidate control channels that thewireless device 18 is supposed to monitor into K subsets, and assigningeach control channel subset to a respective subset of the subframes inthe DRX awake period of the wireless device 18. To facilitate thediscussion, the following symbols are defined:

Symbol Definition P_(k) the power required by the wireless device tomonitor the k^(th) control channel subset using soft DRX n_(k) Number ofsubframes where the wireless device is Awake and it is expected tomonitor the k^(th) control channel subset using soft DRX

One can design soft DRX to ensure that it results in the same or lessenergy while making the wireless device 18 stay awake for longer orsimilar duration compared to legacy DRX by satisfying the followingequations:

Σ_(k=1) ^(K) n _(k) P _(k) ≤n _(legacy) P _(legacy), (Energy constraint)

Σ_(k=1) ^(K) n _(k) ≥n _(legacy). (Awake period constraint)

As noted above, by reducing the number of control channel candidatesmonitored by the wireless device 18 in a particular subframe, the basestation 14 will have less flexibility in scheduling the wireless device18 in that subframe. For instance, if two wireless devices 18 monitoronly the same, single candidate, then these two wireless devices 18cannot be scheduled at the same time in a subframe. Thus, it is expectedthat using soft DRX may lead to reduced scheduling flexibility at thebase station 14 compared to legacy DRX, as soft DRX limits the number ofcontrol channels monitored by the wireless device 18 in some subframes.

In some embodiments, one or more techniques are applied to improve thescheduling flexibility of the base station 14 when soft DRX is used. Inparticular, in some embodiments, different wireless devices 18 ordifferent groups of wireless devices 18 may be configured with differentDRX offsets such that a subframe(s) to which a control channel subsethaving a limited number of candidate control channels is assigned forone wireless device 18 (or one group of wireless devices 18) does notoverlap with a subframe(s) to which the same control channel subset isassigned to another wireless device 18 (or another group of wirelessdevices 18). In this manner, scheduling flexibility is improved.

More specifically, the limit in scheduling flexibility is mainlyobserved in the event when there is more than one wireless device 18that monitor limited and similar control channel subsets at the sametime. To reduce the probability of such an event, the base station 14can properly assign different DRX offsets (drxStartOffset) for differentwireless devices 18, where drxStartOffset is defined as the startingtime with respect to subframe number when the wireless device 18activates the On Duration Timer. To illustrate this, FIGS. 12A and 12Bshow the soft DRX profiles of two wireless devices 18, assuming thatboth wireless devices 18 use the soft DRX profile provided in Example 1and shown in FIG. 11B. It can be seen from FIGS. 12A and 12B that thesecond control subset of the two wireless devices 18 do not overlap byproperly adjusting the drxStartOffset. In this manner, schedulingflexibility is improved.

In some embodiments, another technique that may be used to improvescheduling flexibility when using soft DRX is as follows. Whenever thereis initial uplink or downlink transmission, the Awake state is extendedby starting or re-starting a DRX Inactivity Timer. The rationale behindstarting the DRX Inactivity Timer is that the wireless device 18 islikely to have more uplink/downlink data. During the DRX InactivityTimer, it is advantageous from a scheduling flexibility point of view tomonitor all control channel candidates (i.e., similar to legacy DRX) formost (if not all) of the DRX Inactivity Timer as it is likely that thewireless device 18 will have more uplink/downlink data. Thus, in someembodiments, even when soft DRX is active, the wireless device 18monitors all candidate control channels during the DRX Inactivity Timer.This enables the base station 14 to transmit DCI to the wireless device18 on any of the candidate control channels during the DRX InactivityTimer.

In some embodiments, another technique that may be used to improvescheduling flexibility when using soft DRX is as follows. Since the setof all control channel candidates can be determined by a wirelessdevice's identifier (e.g., using an RNTI in LTE), the base station 14can properly assign different wireless device identifiers for thosewireless devices 18 with soft DRX such that the overlap is minimized forall control channel candidates or at least for the control channelsubset having a limited number of candidate control channels.

Modifying the DRX parameters for legacy DRX is supported in the LTEstandard. This can be done by sending an RRC Reconfiguration messagewith a new DRX configuration. Modifying the DRX parameters for legacyDRX using MAC CEs is also possible. As discussed above, in someembodiments, switching between legacy DRX and soft DRX, e.g., due toparticular events, may be performed using, e.g., either RRC signaling orMAC CEs. For instance, if the base station 14 is overloaded with manywireless devices 18, the base station 14 may request some or all of thewireless devices 18 to switch to legacy DRX in order to have fullscheduling flexibility. In another instance, the base station 14 mayrequest the wireless device 18 to change its soft DRX parameters, suchas the number of control channel subsets. Similarly, the wireless device18 may request a change to its soft DRX parameters due to any event,such as running low on battery power.

FIG. 13 is a schematic block diagram of the wireless device 18 accordingto some embodiments of the present disclosure. As illustrated, thewireless device 18 includes one or more processors 22 (e.g., CentralProcessing Units (CPUs), Application Specific Integrated Circuits(ASICs), Field Programmable Gate Arrays (FPGAs), and/or the like),memory 24, and one or more transceivers 26 each including one or moretransmitters 28 and one or more receivers 30 coupled to one or moreantennas 32. In some embodiments, the functionality of the wirelessdevice 18 described herein may be fully or partially implemented insoftware that is, e.g., stored in the memory 24 and executed by theprocessor(s) 22.

In some embodiments, a computer program including instructions which,when executed by at least one processor, causes the at least oneprocessor to carry out the functionality of the wireless device 18according to any of the embodiments described herein is provided. Insome embodiments, a carrier comprising the aforementioned computerprogram product is provided. The carrier is one of an electronic signal,an optical signal, a radio signal, or a computer readable storage medium(e.g., a non-transitory computer readable medium such as memory).

FIG. 14 is a schematic block diagram of the wireless device 18 accordingto some other embodiments of the present disclosure. The wireless device18 includes one or more modules 34, each of which is implemented inhardware, software, or combinations of both. As an example, in someembodiments, the one or more modules 34 include one or more modules thatoperate to perform the functionality of the wireless device 18 withrespect to the process described above. For example, the modules 34 mayinclude a monitoring module 34-1 that operates to monitor, during a DRXawake period, two or more control channel subsets during two or moretime periods within the DRX awake period, respectively, wherein the twoor more control channel subsets are different subsets of a plurality ofcandidate control channels, as described above. The modules 34 mayinclude additional modules that perform the additional functionality ofthe wireless device 18 described above.

FIG. 15 is a schematic block diagram of a network node 36 according tosome embodiments of the present disclosure. The network node 36 may be,for example, a radio access node such as, for example, a base station 14or a core network node such as, for example, a node in the core network20 of FIG. 3. As illustrated, the network node 36 includes a controlsystem 38 that includes one or more processors 40 (e.g., CPUs, ASICs,FPGAs, and/or the like), memory 42, and a network interface 44. Inaddition, if the network node 36 is a radio access node, then thenetwork node 36 also includes one or more radio units 46 that eachincludes one or more transmitters 48 and one or more receivers 50coupled to one or more antennas 52. In some embodiments, the radiounit(s) 46 is external to the control system 38 and connected to thecontrol system 38 via, e.g., a wired connection (e.g., an opticalcable). However, in some other embodiments, the radio unit(s) 46 andpotentially the antenna(s) 52 are integrated together with the controlsystem 38. The one or more processors 40 operate to provide one or morefunctions of a network node as described herein. In some embodiments,the function(s) are implemented in software that is stored, e.g., in thememory 42 and executed by the one or more processors 40.

FIG. 16 is a schematic block diagram that illustrates a virtualizedembodiment of the network node 36 according to some embodiments of thepresent disclosure. As used herein, a “virtualized” network node (e.g.,a virtualized base station or a virtualized radio access node) is animplementation of the network node in which at least a portion of thefunctionality of the network is implemented as a virtual component(e.g., via a virtual machine(s) executing on a physical processingnode(s) in a network(s)). As illustrated, in this example, the networknode 36 may include the control system 38 that includes the one or moreprocessors 40 (e.g., CPUs, ASICs, FPGAs, and/or the like), the memory42, and the network interface 44 and, depending on the type of networknode, the one or more radio units 46 that each includes the one or moretransmitters 48 and the one or more receivers 50 coupled to the one ormore antennas 52, as described above. The control system 38 is connectedto the radio unit(s) 46 via, for example, an optical cable or the like.The control system 38 is connected to one or more processing nodes 54coupled to or included as part of a network(s) 56 via the networkinterface 44. Each processing node 54 includes one or more processors 58(e.g., CPUs, ASICs, FPGAs, and/or the like), memory 60, and a networkinterface 62.

In this example, functions 64 of the network node 36 (e.g., functions ofthe base station 14) described herein are implemented at the one or moreprocessing nodes 54 or distributed across the control system 38 and theone or more processing nodes 54 in any desired manner. In someparticular embodiments, some or all of the functions 64 of the networknode 36 described herein are implemented as virtual components executedby one or more virtual machines implemented in a virtual environment(s)hosted by the processing node(s) 54. As will be appreciated by one ofordinary skill in the art, additional signaling or communication betweenthe processing node(s) 54 and the control system 38 is used in order tocarry out at least some of the desired functions 64. Notably, in someembodiments, the control system 38 may not be included, in which casethe radio unit(s) 46 communicate directly with the processing node(s) 54via an appropriate network interface(s). Further, in embodiments inwhich the network node 36 is not a radio access node (e.g., a corenetwork node), then the network node 36 may be entirely virtualized(i.e., there may be no control system 38 or radio unit(s) 46.

In some embodiments, a computer program including instructions which,when executed by at least one processor, causes the at least oneprocessor to carry out the functionality of a network node or a node(e.g., a processing node 54) implementing one or more of the functions64 of the network node in a virtual environment according to any of theembodiments described herein is provided. In some embodiments, a carriercomprising the aforementioned computer program product is provided. Thecarrier is one of an electronic signal, an optical signal, a radiosignal, or a computer readable storage medium (e.g., a non-transitorycomputer readable medium such as memory).

FIG. 17 is a schematic block diagram of the network node 36 according tosome other embodiments of the present disclosure. The network node 36includes one or more modules 66, each of which is implemented inhardware, software, or combinations of both. The module(s) 66 providethe functionality of the network node 36 described herein. For example,the module(s) 66 may include one or modules that perform the operationsof the base station 14 described above. In particular, the module(s) 66may include a transmission module 66-1 operable to initiatetransmission, during a DRX awake period of a wireless device 18, of DCIto the wireless device 18 in a time period within the DRX awake periodof the wireless device 18 on one or more control channels in one of atleast two control channel subsets, wherein the at least two controlchannel subsets are at least two different subsets of a plurality ofcandidate control channels that are configured for the wireless device18 for at least two time periods within the DRX awake period of thewireless device (18), respectively.

The following acronyms are used throughout this disclosure.

-   -   μs Microsecond    -   3GPP Third Generation Partnership Project    -   5G Fifth Generation    -   ASIC Application Specific Integrated Circuit    -   CA Carrier Aggregation    -   CE Control Element    -   CPU Central Processing Unit    -   DCI Downlink Control Information    -   DRX Discontinuous Reception    -   eNB Enhanced or Evolved Node B    -   EPC Evolved Packet Core    -   ePDCCH Enhanced Physical Downlink Control Channel    -   EUTRAN Evolved Universal Terrestrial Radio Access Network    -   FPGA Field Programmable Gate Array    -   kHz Kilohertz    -   LTE Long Term Evolution    -   MAC Medium Access Control    -   MME Mobility Management Entity    -   ms Millisecond    -   MTC Machine Type Communication    -   OFDM Orthogonal Frequency Division Multiplexing    -   PDCCH Physical Downlink Control Channel    -   PDN Packet Data Network    -   PDSCH Physical Downlink Shared Channel    -   P-GW Packet Data Network Gateway    -   PRB Physical Resource Block    -   RAN Radio Access Network    -   RE Resource Element    -   RNTI Radio Network Temporary Identifier    -   RRC Radio Resource Control    -   SCEF Service Capability Exposure Function    -   S-GW Serving Gateway    -   TR Technical Report    -   TS Technical Specification    -   UE User Equipment

Those skilled in the art will recognize improvements and modificationsto the embodiments of the present disclosure. All such improvements andmodifications are considered within the scope of the concepts disclosedherein and the claims that follow.

1. A method of operation of a node in a wireless communications network,the method comprising: initiating transmission, during a DiscontinuousReception (DRX) awake period of a wireless device, of controlinformation to the wireless device in a time period within the DRX awakeperiod of the wireless device on one or more control channels from oneof at least two control channel subsets, wherein the at least twocontrol channel subsets are at least two different subsets of aplurality of candidate control channels that are configured for thewireless device for at least two time periods within the DRX awakeperiod of the wireless device, respectively.
 2. The method of claim 1,wherein the at least two time periods are two or more subframes.
 3. Themethod of claim 1, wherein: the plurality of candidate control channelscomprises a first plurality of candidate Physical Downlink ControlChannels (PDCCHs) and a second plurality of candidate enhanced PDCCHs(ePDCCHs); and the at least two control channel subsets comprise: afirst control channel subset that comprises at least some of the firstplurality of candidate PDCCHs but not any of the second plurality ofcandidate ePDCCHs; and a second control channel subset that comprises atleast some of the second plurality of candidate ePDCCHs but not any ofthe first plurality of candidate PDCCHs.
 4. The method of claim 1,wherein the at least two control channel subsets consist of two controlchannel subsets.
 5. The method of claim 1, wherein the at least twocontrol channel subsets comprise a first control channel subset thatcomprises all of the plurality of candidate control channels and asecond control channel subset that comprises less than all of theplurality of candidate control channels.
 6. The method of claim 1,wherein initiating the transmission of the control information to thewireless device in the time period within the DRX awake period of thewireless device on said one or more control channels in the one of theat least two control channel subsets comprises: determining a firstcontrol channel subset for a first time period within the DRX awakeperiod of the wireless device; initiating the transmission of thecontrol information to the wireless device in one or more candidatecontrol channels in the first control channel subset during the firsttime period if the wireless device is scheduled in the first timeperiod; determining a second control channel subset for a second timeperiod within the DRX awake period of the wireless device; andinitiating the transmission of the control information to the wirelessdevice in one or more candidate control channels in the second controlchannel subset during the second time period if the wireless device isscheduled in the second time period.
 7. The method of claim 1, furthercomprising: initiating transmission of one or more soft DRX parametersto the wireless device, the one or more soft DRX parameters comprisinginformation that defines the at least two control channel subsets forthe at least two time periods within the DRX awake period, respectively.8. A node for operation in a wireless communications network, the nodecomprising: at least one processor; and memory storing instructionsexecutable by the at least one processor whereby the node is operableto: initiate transmission, during a Discontinuous Reception (DRX) awakeperiod of a wireless device, of control information to the wirelessdevice in a time period within the DRX awake period of the wirelessdevice on one or more control channels from one of at least two controlchannel subsets, wherein the at least two control channel subsets are atleast two different subsets of a plurality of candidate control channelsthat are configured for the wireless device for at least two timeperiods within the DRX awake period of the wireless device,respectively.
 9. The node of claim 8, wherein the at least two timeperiods are two or more subframes.
 10. The node of claim 8, wherein: theplurality of candidate control channels comprises a first plurality ofcandidate Physical Downlink Control Channels (PDCCHs) and a secondplurality of candidate enhanced PDCCHs (ePDCCHs); and the at least twocontrol channel subsets comprise: a first control channel subset thatcomprises at least some of the first plurality of candidate PDCCHs butnot any of the second plurality of candidate ePDCCHs; and a secondcontrol channel subset that comprises at least some of the secondplurality of candidate ePDCCHs but not any of the first plurality ofcandidate PDCCHs.
 11. The node of claim 8, wherein the at least twocontrol channel subsets consist of two control channel subsets.
 12. Thenode of claim 8, wherein the at least two control channel subsetscomprise a first control channel subset that comprises all of theplurality of candidate control channels and a second control channelsubset that comprises less than all of the plurality of candidatecontrol channels.
 13. The node of claim 8, wherein to initiate thetransmission of the control information to the wireless device in thetime period within the DRX awake period of the wireless device on saidone or more control channels in the one of the at least two controlchannel subsets, the node is further operable to: determine a firstcontrol channel subset for a first time period within the DRX awakeperiod of the wireless device; initiate the transmission of the controlinformation to the wireless device in one or more candidate controlchannels in the first control channel subset during the first timeperiod if the wireless device is scheduled in the first time period;determine a second control channel subset for a second time periodwithin the DRX awake period of the wireless device; and initiate thetransmission of the control information to the wireless device in one ormore candidate control channels in the second control channel subsetduring the second time period if the wireless device is scheduled in thesecond time period.
 14. The node of claim 8, further operable to:initiate transmission of one or more soft DRX parameters to the wirelessdevice, the one or more soft DRX parameters comprising information thatdefines the at least two control channel subsets for the at least twotime periods within the DRX awake period, respectively.
 15. Anon-transitory computer-readable storage medium comprising instructionsfor operation of a node in a wireless communications network, whereinthe instructions, upon execution by a processor of the node, cause thenode to: initiate transmission, during a Discontinuous Reception (DRX)awake period of a wireless device, of control information to thewireless device in a time period within the DRX awake period of thewireless device on one or more control channels from one of at least twocontrol channel subsets, wherein the at least two control channelsubsets are at least two different subsets of a plurality of candidatecontrol channels that are configured for the wireless device for atleast two time periods within the DRX awake period of the wirelessdevice, respectively.
 16. The non-transitory computer-readable storagemedium of claim 15, wherein the instructions further cause the node tolimit the transmission of the control information to the wireless deviceon control channels of the one or more control channels that are beingmonitored by the wireless device.
 17. The non-transitorycomputer-readable storage medium of claim 15, wherein the at least twotime periods are two or more subframes.
 18. The non-transitorycomputer-readable storage medium of claim 15, wherein the at least twocontrol channel subsets consist of two control channel subsets.
 19. Thenon-transitory computer-readable storage medium of claim 15, wherein theat least two control channel subsets comprise a first control channelsubset that comprises all of the plurality of candidate control channelsand a second control channel subset that comprises less than all of theplurality of candidate control channels.
 20. The non-transitorycomputer-readable storage medium of claim 15, wherein to initiate thetransmission of the control information to the wireless device in thetime period within the DRX awake period of the wireless device on saidone or more control channels in the one of the at least two controlchannel subsets, the instructions further cause the node to: determine afirst control channel subset for a first time period within the DRXawake period of the wireless device; initiate the transmission of thecontrol information to the wireless device in one or more candidatecontrol channels in the first control channel subset during the firsttime period if the wireless device is scheduled in the first timeperiod; determine a second control channel subset for a second timeperiod within the DRX awake period of the wireless device; and initiatethe transmission of the control information to the wireless device inone or more candidate control channels in the second control channelsubset during the second time period if the wireless device is scheduledin the second time period.